Experience with cultured human fibroblasts (CHF) from patients with cholesterol ester storage disease suggested that CHF might be of value in the study of familial hypercholesterolemias (FH). In the present study, total lipid and neutral lipid composition of CHF has been examined in comparison with electron microscopy of the same cells. The CHF were grown in McCoy's 5a Medium with 30 percent fetal calf serum, 8-12 days (confluence). No significance occurred in the lipid composition of CHF from normal and FH individuals when grown in the presence of 30 percent fetal calf serum. The ultrastructural features of these cells are still under study.